A nanofiltration (NF) membrane pilot plant was tested to treat water from a spring located in the Tula Valley. Conventional physicochemical parameters and the pathogenic content were analyzed at the inlet and outlet (permeate) of the process. Ninety-five per cent removal of heterotrophic bacteria was obtained by the membrane and complete removal of all other pathogens was achieved. The membrane process performed better than the municipal chlorination facility. The NF process also removed most of the organic matter and removal of emerging pollutants varied from 5 to 100%, depending on the compound. A softening process prevented the membrane system from clogging, and continuous operation was carried out for more than 1 month with minimal maintenance.